Fix imeLayerAndImeSnapshotVisibleOnScreen flaky

In case IME-snapshot removed and the assertion can't verify IME-snapshot
visible from the next frame, fix the assertion by verifying both
IME-snapshot and IME are invisible in the end.

Fix: 228947097
Test: atest FlickerTests:CloseImeEditorPopupDialogTest \
         --rerun-until-failure 20
Change-Id: I1d945cd10761af1c7dad9154a550e69bf4d481ee